Ellipsis Modelling

Scott DyksterhuisDietmar Müller, Louis Moresi and Patrice Rey

University of Sydney

Geodynamics

Combined mantle convection and plate kinematic modelling Palaeostress modelling

Dynamic basin modelling(mantle convection, lithos-pheric thinning, sedimentation/erosion)

Basin history

Put constraints on tectonic/thermalhistory of deep sedimentary sections

Constrain timing of fault reactivation bycombining palaeo-stress modelling withobservations from seismic data

Seismic and well data integration and interpretation

LithologiesPhysical propertiesBiostratigraphyBasin geometryFaulting through time

Geological modeling is associated with a different set of requirements:

• Very large deformation of solid materials including• accurate tracking of material (compositional) interfaces –

melt?• accurate tracking of history variables • evolution of oriented structure• etc…

• Only want a tool to fit data/concepts (geometry, thermal history, potential field)

• Easy use and implement

Ellipsis

• A particle-in-cell finite element code that solves 2D and 3D fluid mechanics problems with & w/o heat transfer, e.g.,– Mantle convection– Lithospheric deformation– subduction

• Ellipsis works with a multigrid solver, which allows quite rapid solutions (but does constrain allowable mesh geometry)

• Solid-like materials can be given higher viscosities than fluid-like materials, or material properties can depend on temperature, depth, pressure, strain, strain rates, etc.

Ellipsis GUI

• Java based GUI for easy interaction with existing models or for creating new ones

• Allows for more complicated geometries – can even use drawings (based on seismic, reconstructions etc) to create models

• Handles all scaling automatically so user can do as much/little as they want

Ellipsis3D…

Interactive Inversion - Nimrod

• NIMROD, NIMROD/G manage the distribution of parameter-space studies on clusters / grids

– robust job distribution

– secure

– visual feedback / portal

• NIMROD/O contains a number of objective inversion algorithms to reduce the number of models evaluated

– Models are cached

– Multiple inversions to help avoid local minima

Initial Conditions

• Evolution of the geotherm through time…• Rheology• Strain rate

Initial Conditions

Fernandez & Ranalli, 1997

Lower Crustal Strength Models

• Relatively high lower crustal strength

Wijns, in press

Lower Crustal Strength Models

• Relatively low lower crustal strength

Wijns, in press

4 Layer models

Strong upper mantle lithosphere

• Distributed

• Core complex

Mantle Rheology

Juxtaposed Craton

• Relatively strong “craton”

Artemieva & Mooney 2001

Conclusions

• Initial constrains extremely important– temperature– rheology

• Modelling not ready for applied examples?

• Accessibility of code important – get the geologist using the modelling software

A student’s perspective…

• Need to have some kind of online materials (rheology) database – Initial conditions

• A permanent web presence/meeting point (wiki site):– Codes, manuals, (benchmark) results (corner store)– community collaboration and “sounding ground”– centralised location for groups to benchmark

codes/results – location for observationalists to pose “challenges”– data